<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        
        /*
        私有属性写在构造函数里面
        公共属性写在原型上
        */
        function Teacher(name, age, id) {
            this.name = name;
            this.age = age;
            this.id = id;
        }
        Teacher.prototype.showID = function() {
            alert(this.id);
        };
        

    </script>
</body>
</html>